Such lamp assemblies are available in a wide variety of variants, especially for illuminating building interiors. The lamp assemblies cast their light cones upon the floor surfaces of the building and generally are mounted in ceilings or at other upper levels in the structure. They can be mounted on the roof or in the roof structures as well. It should be understood, however, that such lamps may be mounted on walls of the building to illuminate floor and wall regions and can, if desired or required, be mounted on exterior surfaces of a building.
Where a view of the lamp or light source is not desirable, the lamp opening may be provided with a lens or diffuser and frequently a dark light reflector can be provided on the light source or in the lamp housing. Reflectors do tend to make the light cone reasonably well defined and do limit losses from the region in which maximum illumination is to occur. The lamp may also be provided with a diaphragm or other shield surrounding the opening from which the light emerges to assist in making the light cone sharp and in maintaining the region beyond the light cone free from illumination or in shadow.
A dark light reflector has the advantage, in addition, that the light source within the housing cannot easily be distinguished.
At the opening to the housing, gridlike structures which may have straight or curved surfaces can be provided as light guides and to mask the lamp or other light emitting structure within the housing.
Diffusers do not have effects similar to those of conventional dark light reflectors and it is difficult with such diffusers to obtain the advantages of dark light reflectors in illuminating lamps.
German Patent document DE-OS 1 497 293 discloses a light distributing plate at the outlet of a lamp housing which is formed with prismatic elements and which deflect and reflect the light from the source and thereby mask the source and distribute the light as may be required.
In a catalog of the assignee of the present application issued in the years 2000/2001 and entitled “Lighting Program” page 340, a prismatic lens is provided to close a lamp housing. The lens plate here has prismatic elements similar to those of DE-OS 1 497 293, although the prism points are slightly rounded. The use of this lens plate is intended to generate a brightening effect with a decorative purpose and, while the lamp within the housing is shielded, a multiplicity of light points can be readily noted in the housing closure element.